1. Field of the Invention
The present invention relates to a high-frequency device mainly used for a high-frequency band radio device or high-frequency band radar device or the like, and more particularly, to a semiconductor device provided with a spiral inductor on a semiconductor substrate.
2. Background Art
In recent years, mobile communication devices typified by portable terminals or the like are required to realize a size reduction, multiple functions and a cost reduction, and high-frequency devices mounted thereon are also required to realize a size reduction, multiple functions and a cost reduction. For such high-frequency devices, an MMIC (Monolithic Microwave Integrated Circuit) is often used in which an active element such as a transistor and a matching circuit are integrally formed on a semi-insulating substrate such as GaAs, SiGe or Si.
A matching circuit is configured of passive elements such as resistor, MIM capacitor, and spiral inductor. The MIM capacitor is made up of an upper layer metal and a lower layer metal of a dielectric film. The spiral inductor is a spiral wire. Since the spiral inductor occupies a greater area than other passive circuits in a matching circuit formed on a semiconductor substrate in particular, the spiral inductor is required to realize a size reduction.
In order to obtain a greater inductance with a small area, a structure is disclosed in which two spiral inductors wound in the same direction are laminated and one spiral inductor is disposed at a position facing a gap with the other (e.g., see Japanese Patent Application Laid-Open No. 2003-78017 (page 5, FIG. 1), Japanese Patent Application Laid-Open No. 2013-153011 (page 6, FIG. 1), Japanese Patent Application Laid-Open No. 11-154730 (page 8, FIG. 1)).
Moreover, as for portable terminals, a same terminal often uses different frequency bands. Therefore, such a terminal needs to use a filter to remove signals in other frequency bands, and requires a matching circuit that forms this filter (e.g., see Japanese Patent Application Laid-Open No. 2007-318362 (page 12, FIG. 2)).